The present invention relates to a cordless or wireless telephone system constituted by a base communication unit which is connected to a telephone line connection, and a portable communication unit which is connected to the base unit by a wireless communication link.
A prior art cordless telephone system usually comprises a base communication unit and a corresponding portable communication unit, and the portable unit performs battery saving (BS) operation at a specific period in order to enhance the service life of battery adapted to power the portable unit. This, however, brings about a drawback that a plurality of telephone lines cannot be used at a time unless the same number of cordless telephone systems as the telephone lines are installed. Another problem is that the total power saving performance attainable with the prior art system is limited because the BS operations of the independent portable units occur at the same period and at entirely different timings.